Its real purpose was to help fill the afternoon viewing hours which had, after years of lobbying by the broadcasters, been freed by Edward Heath’s Conservative government from the ghetto of schools’ programmes.

Today, exactly 45 years after the opening episode went out, its first star recalled how little confidence in its longevity there had been.

“My first contract was for just 12 episodes,” said Frazer Hines, then a veteran of Doctor Who, who had signed on as Joe Sugden, younger brother to Jack, the returning roué who had inherited the farm.

“It was just another job, really. But after a few weeks, one of the production assistants told us she had just seen the script for episode 26 - and all of a sudden we knew it could run.”

Kathy Glover (Malandra Burrows) looks in terror moments before becoming the victim of a hit and run, in 1998

But he added: “Even then, the contract was still only for two years. They realised some of the companies could just take it off.”

In the days when ITV regions screened many programmes on different days, or not at all, the new afternoon schedule in 1972 was a rare example of co-operation, with drama, chat shows and the country’s first regular lunchtime news.

“Each weekday company,” Thames Television’s director of programmes, Brian Tesler, told TV Times, “has provided a programme that is appropriate to its own area. These are aimed at the daytime audiences, which are predominantly female.”

But Emmerdale - the only programme from the schedule to survive beyond the 1970s, quickly found a broader audience and began to migrate, one region at a time, from afternoons to the peak-time evening schedule.

Today, the franchise is one of the most valuable in ITV, with six episodes a week instead of just two, and two visitor attractions in Leeds.

Mr Hines and his former co-star, actress Malandra Burrows - both of whose characters were written out long ago - were at one of the tourist centres yesterday, the former car showroom on Burley Road in Leeds in which interior scenes used to be filmed.

A scale model of the fictional Emmerdale village has been built there, along with a life-size reproduction of the Woolpack pub and other sets from the series.

Mr Hines, a native of Hors­forth, Leeds, who now breeds racehorses in Lincolnshire, said he had landed the role that was to dominate his life, on and off, for the next 22 years, on the recommendation of his former girlfriend, the actress Liza God­dard, whose father, David, was Emmerdale’s first producer.

“I was having Sunday lunch with her family, and he said he was going to do a 12-part series in Yorkshire for the housewives,” Mr Hines said.

“He was looking for someone to play the younger son, and Liza said, ‘He’s sitting right opposite you,dad - and if you don’t cast him, mum and I are leaving home’.”

After two years, the popularity of the show had risen to such an extent that when Joe Sugden married his fiancée Christine, it finally became headline news in TV Times.

Emmerdale has been filmed at various locations in Yorkshire, including the villages of Leathley and Esholt, but its present 300-acre exterior at Harewood is the biggest ever built in Britain.

The site is open to visitors at weekends, alongside the full-time “studio tour” in one of the buildings near ITV’s main studio centre in Leeds.

Actress Malandra Burrows, who joined Frazer Hines there to celebrate the show’s 45th anniversary, last appeared 12 years ago, by which time she had seen three husbands killed.

Mr Hines said he had been invited back after the end of his first marriage in 1984.

“You’re not having much luck with real women so come back and join your other family,” he said he had been told.